[PATCH v2 8/8] gpio: ws16c48: Implement get_multiple callback

[William Breathitt Gray]

The WinSystems WS16C48 device provides 48 lines of digital I/O accessed
via six 8-bit ports. Since eight input lines are acquired on a single
port input read, the WS16C48 GPIO driver may improve multiple input
reads by utilizing a get_multiple callback. This patch implements the
ws16c48_gpio_get_multiple function which serves as the respective
get_multiple callback.

Signed-off-by: William Breathitt Gray <vilhelm.g...@gmail.com>
---
 drivers/gpio/gpio-ws16c48.c | 46 +++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 46 insertions(+)

diff --git a/drivers/gpio/gpio-ws16c48.c b/drivers/gpio/gpio-ws16c48.c
index 746648244bf3..9f2e7d0b48f9 100644
--- a/drivers/gpio/gpio-ws16c48.c
+++ b/drivers/gpio/gpio-ws16c48.c
@@ -129,6 +129,51 @@ static int ws16c48_gpio_get(struct gpio_chip *chip, 
unsigned offset)
        return !!(port_state & mask);
 }
 
+static int ws16c48_gpio_get_multiple(struct gpio_chip *chip,
+       unsigned long *mask, unsigned long *bits)
+{
+       struct ws16c48_gpio *const ws16c48gpio = gpiochip_get_data(chip);
+       const unsigned int gpio_reg_size = 8;
+       size_t i;
+       const size_t num_ports = chip->ngpio / gpio_reg_size;
+       unsigned int bits_offset;
+       size_t word_index;
+       unsigned int word_offset;
+       unsigned long mask_word;
+       const unsigned long port_mask = GENMASK(gpio_reg_size, 0);
+       unsigned long port_state;
+
+       /* clear bits array to a clean slate */
+       bitmap_zero(bits, chip->ngpio);
+
+       /* get bits are evaluated a gpio port register at a time */
+       for (i = 0; i < num_ports; i++) {
+               /* gpio offset in bits array */
+               bits_offset = i * gpio_reg_size;
+
+               /* word index for bits array */
+               word_index = BIT_WORD(bits_offset);
+
+               /* gpio offset within current word of bits array */
+               word_offset = bits_offset % BITS_PER_LONG;
+
+               /* mask of get bits for current gpio within current word */
+               word_mask = mask[word_index] & (port_mask << word_offset);
+               if (!word_mask) {
+                       /* no get bits in this port so skip to next one */
+                       continue;
+               }
+
+               /* read bits from current gpio port */
+               port_state = inb(ws16c48gpio->base + i);
+
+               /* store acquired bits at respective bits array offset */
+               bits[word_index] |= port_state << word_offset;
+       }
+
+       return 0;
+}
+
 static void ws16c48_gpio_set(struct gpio_chip *chip, unsigned offset, int 
value)
 {
        struct ws16c48_gpio *const ws16c48gpio = gpiochip_get_data(chip);
@@ -383,6 +428,7 @@ static int ws16c48_probe(struct device *dev, unsigned int 
id)
        ws16c48gpio->chip.direction_input = ws16c48_gpio_direction_input;
        ws16c48gpio->chip.direction_output = ws16c48_gpio_direction_output;
        ws16c48gpio->chip.get = ws16c48_gpio_get;
+       ws16c48gpio->chip.get_multiple = ws16c48_gpio_get_multiple;
        ws16c48gpio->chip.set = ws16c48_gpio_set;
        ws16c48gpio->chip.set_multiple = ws16c48_gpio_set_multiple;
        ws16c48gpio->base = base[id];
-- 
2.16.2